U.S. patent application number 10/171133 was filed with the patent office on 2003-08-07 for method and apparatus for measuring half frequency whirl in a spindle motor.
Invention is credited to Lim, ChoonKiat, Liu, Xiong, Tang, YongJie, Yong, Pow-Hing.
Application Number | 20030146766 10/171133 |
Document ID | / |
Family ID | 27668191 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030146766 |
Kind Code |
A1 |
Liu, Xiong ; et al. |
August 7, 2003 |
Method and apparatus for measuring half frequency whirl in a
spindle motor
Abstract
An apparatus and method of indirectly measuring half frequency
whirl in a spindle motor having a rotor adapted to rotate a disc
having a track which is followed by a transducer head that is
actuated by a control system is provided. Vibration signals
produced at the transducer head while the transducer head follows
the track are detected. The half frequency whirl is determined as a
function of the detected vibration signals.
Inventors: |
Liu, Xiong; (Singapore,
SG) ; Lim, ChoonKiat; (Singapore, SG) ; Tang,
YongJie; (Singapore, SG) ; Yong, Pow-Hing;
(Singapore, SG) |
Correspondence
Address: |
Alan G. Rego
WESTMAN CHAMPLIN & KELLY
International Centre - Suite 1600
900 South Second Avenue
Minneapolis
MN
55402-3319
US
|
Family ID: |
27668191 |
Appl. No.: |
10/171133 |
Filed: |
June 13, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60355622 |
Feb 5, 2002 |
|
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|
Current U.S.
Class: |
324/545 ; 360/69;
G9B/19.027; G9B/21.02; G9B/33.024; G9B/5.221 |
Current CPC
Class: |
G11B 33/08 20130101;
G11B 5/59627 20130101; G11B 21/106 20130101; G11B 7/0953 20130101;
G11B 19/20 20130101 |
Class at
Publication: |
324/545 ;
360/69 |
International
Class: |
G11B 015/18 |
Claims
What is claimed is:
1. A method of indirectly measuring half frequency whirl in a
spindle motor having a rotor adapted to rotate a disc having a
track which is followed by a transducer head that is actuated by a
control system, the method comprising: (a) detecting vibration
signals produced at the transducer head while the transducer head
follows the track; and (b) determining the half frequency whirl as
a function of the detected vibration signals.
2. The method of claim 1 wherein the detecting vibration signals
step (a) is carried out using a non-contact vibration sensing
technique.
3. The method of claim 2 wherein using the non-contact vibration
sensing technique includes focusing a laser beam on an actuator
that supports the transducer head, and measuring a reflection of
the laser beam from the actuator.
4. The method of claim 3 wherein the laser beam is focused on a
mirror mounted on the actuator.
5. The method of claim 2 wherein a Laser Doppler Vibrometer is
employed to implement the non-contact vibration sensing
technique.
6. The method of claim 1 wherein the determining the half frequency
whirl step (b) comprises obtaining a frequency spectrum of the
detected vibration signals.
7. The method of claim 6 wherein the frequency spectrum of the
detected vibration signals is obtained by utilizing a spectrum
analyzer.
8. The method of claim 1 wherein the spindle motor is a part of a
disc drive storage system and wherein the method is carried out
with the spindle motor installed in the disc drive storage
system.
9. The method of claim 1 wherein the spindle motor is a part of a
disc drive tester and wherein the method is carried out with the
spindle motor installed in the disc drive tester.
10. The method of claim 1 further comprising (c) comparing the
determined half frequency whirl with a threshold half frequency
whirl value.
11. A apparatus for indirectly measuring half frequency whirl in a
spindle motor having a rotor adapted to rotate a disc having a
track which is followed by a transducer head that is actuated by a
control system, the apparatus comprising: a vibration sensor
configured to detect vibration signals produced at the transducer
head while the transducer head follows the track; and an analyzer
configured to determine the half frequency whirl as a function of
the detected vibration signals.
12. The apparatus of claim 11 wherein the vibration sensor is a
non-contact vibration sensor.
13. The apparatus of claim 12 wherein the non-contact vibration
sensor is configured to focus a laser beam on an actuator that
supports the transducer head, and to measure a reflection of the
laser beam from the actuator.
14. The apparatus of claim 13 wherein the non-contact vibration
sensor is configured to focus the laser beam on a mirror mounted on
the actuator.
15. The apparatus of claim 12 wherein the vibration sensor is a
Laser Doppler Vibrometer.
16. The apparatus of claim 11 wherein the analyzer is a spectrum
analyzer configured to obtain a frequency spectrum of the detected
vibration signals.
17. The apparatus of claim 11 wherein the spindle motor is a part
of a disc drive storage system.
18. The apparatus of claim 11 wherein the spindle motor is a part
of a disc drive tester.
19. The apparatus of claim 11 further comprising a processor
configured to compare the determined half frequency whirl with a
threshold half frequency whirl value.
20. A apparatus for indirectly measuring half frequency whirl in a
spindle motor having a rotor adapted to rotate a disc having a
track which is followed by a transducer head that is actuated by a
control system, the apparatus comprising: a vibration sensor
configured to detect vibration signals produced at the transducer
head while the transducer head follows the track; and means for
determining the half frequency whirl as a function of the detected
vibration signals.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Provisional
Application No. 60/355,622 filed on Feb. 5, 2002 for inventors
Xiong Liu, ChoonKiat Lim, Yongjie Tang and Pow-Hing Yong and
entitled "METHOD AND APPARATUS FOR MEASURING FDB MOTOR HALF
FREQUENCY WHIRL."
FIELD OF THE INVENTION
[0002] The present invention relates to spindle motors used in
applications such as disc drive data storage systems. In
particular, the present invention relates to measuring half
frequency whirl vibrations that occur in spindle motors.
BACKGROUND OF THE INVENTION
[0003] Spindle motors are commonly used in various applications
wherein a precise rotating movement is required. These applications
include disc drive data storage systems and their test apparatus
(spin-stands). These disc drives and spin-stand testers usually
incorporate one or more discs mounted for rotation on a rotor of
the spindle motor. Data is recorded and read from a plurality of
concentric tracks on the discs by an array of read/write heads. The
heads are typically moved radially from track to track on the disc
by an actuator assembly.
[0004] Advances in disc drive technology have revolved around
reducing the size of disc drive components and the size of the
overall disc drive. Smaller disc drives can allow for a reduction
in overall size of computer systems into which disc drives are
installed. With the reduction in size of the disc drive, more space
is available within the computer system for other components. In
addition to small disc drives, the disc drive industry has also
made advances toward increasing the storage capacity of individual
disc drive units.
[0005] The reduction in size of the disc drive can compound certain
problems often associated with various operational features of disc
drives. It also places greater performance demands on spin-stands
used to test various components of the drive. One such problem
involves vibrations or harmonic oscillations in the disc drive and
spin-stand tester. The effect of vibrations and oscillations has
become magnified as the size of the drive is reduced and data
tracks are spaced closer together. As a result, the overall
performance of the drive and spin-stand are negatively
impacted.
[0006] One source of vibration in a disc drive and a spin-stand is
from the spindle motors that they employ. These spindle motors
typically include a stator comprising a core having windings
arranged thereabout and a rotor shaft. Bearings support the rotor
shaft in the radial and axial directions, the bearings being
lubricated by a fluid. Large amplitude vibration can be caused by
imbalance, rotor shaft flexibility, bearing flexibility, fluid film
forces in the bearings as the shaft rotates, etc. One particularly
common vibration mode occurs at approximately half the shaft
rotation frequency. This vibration mode is called half frequency
whirl. This half frequency whirl phenomenon is especially prominent
in motors that use fluid dynamic bearings. Obtaining precise
measurements of half frequency whirl is useful for design
verification, quality assurance and failure analysis of spindle
motors and disc drives and spin-stand testers which include these
motors.
[0007] Various direct and indirect measurement techniques have been
employed to determine half frequency whirl in a spindle motor. One
direct measurement technique used to determine half frequency whirl
includes placing a capacitance probe near the outer surface of the
rotor shaft of the spindle motor to measure changes in position of
the shaft while it rotates. These position measurements from the
capacitance probe are fed to a spectrum analyzer that computes a
frequency spectrum of the position measurements. The magnitude of
the half frequency whirl is obtained from the frequency spectrum.
Since the outer surface of the rotor shaft is not perfectly smooth
and the resolution of a capacitance probe is relatively low, the
half frequency whirl determined from such measurements is
imprecise.
[0008] One indirect measurement technique for determining half
frequency whirl includes utilizing proximity displacement probes to
measure the radial motion of an edge of a disc that is mounted on
the rotor shaft of the spindle motor instead of directly measuring
rotor shaft motion. The half frequency whirl is determined as a
function of these measurements. However, due to disc manufacturing
and assembling errors, such as imperfection in disc roundness and
misalignment between the disc and the rotor shaft, the half
frequency whirl determined from such measurements is inaccurate.
Other current direct and indirect half frequency whirl measurement
techniques have similar disadvantages.
[0009] Embodiments of the present invention provide solutions to
these and other problems, and offer other advantages over the prior
art.
SUMMARY OF THE INVENTION
[0010] An apparatus and method of indirectly measuring half
frequency whirl in a spindle motor having a rotor adapted to rotate
a disc having a track which is followed by a transducer head that
is actuated by a control system is provided. Vibration signals
produced at the transducer head while the transducer head follows
the track are detected. The half frequency whirl is determined as a
function of the detected vibration signals.
[0011] Other features and benefits that characterize embodiments of
the present invention will be apparent upon reading the following
detailed description and review of the associated drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1-1 is a block diagram showing an apparatus for
indirectly measuring half frequency whirl in a spindle motor in
accordance with the present invention.
[0013] FIG. 1-2 illustrates a top view of the actuator and the disc
shown in the block diagram of FIG. 1-1.
[0014] FIG. 2-1 is a perspective view of a disc drive and a half
frequency whirl measurement apparatus.
[0015] FIG. 2-2 is a block diagram of a servo loop of the disc
drive of FIG. 2-1.
[0016] FIG. 2-3 is a plot of a the sensitivity function of the
servo loop of FIG. 2-2.
[0017] FIGS. 2-4 and 2- 5 illustrate a comparison between frequency
spectrums obtained using a prior art rotor vibration measurement
technique and a rotor vibration measurement technique of the
present invention.
[0018] FIG. 3 is a perspective view of a spin-stand tester and a
half frequency whirl measurement apparatus.
[0019] FIG. 4 is a flow chart representing a method of indirectly
measuring half frequency whirl in a spindle motor in accordance
with an illustrative embodiment of the present invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0020] Referring now to FIG. 1-1, an apparatus 100 for indirectly
measuring half frequency whirl in a spindle motor 106 is shown. The
same reference numerals are used in various figures to represent
the same or similar elements. Spindle motor 106 includes a stator
108, which includes a core having windings arranged thereabout, and
a rotor shaft 110. Spindle motor 106 also includes bearings 112
that support rotor shaft 110 in radial and axial directions.
Bearings 112 are typically lubricated by a fluid.
[0021] A disc 114, mounted about rotor shaft 110, has a disc
surface that includes at least one track such as 117 (shown in FIG.
1-2). A transducer head included in a slider 116, which is
supported by an actuator 118, communicates with the disc surface. A
controller 120 provides actuation signals, via control line 124, to
actuator 118 for positioning slider 116 over a desired track such
as 117. Positioning of slider 116 over track 117 is typically
carried out by a closed-loop servo control technique. Communication
between controller 120 and head 116 takes place via control line
126. The operation of spindle motor 106 is controlled by signals
provided by controller 120 via control line 128.
[0022] Energization of spindle motor 106 causes shaft 110 and disc
114 to rotate. Usually, when disc 114 rotates, head 116 flies above
disc 114 on thin films of air or liquid that carry head 116 for
communicating with the disc surface. Instead of flying above disc
114, head 116 may remain in contact with the disc surface when disc
114 rotates. As mentioned above, shaft 110 vibrates as it rotates,
and one particularly common vibration mode, referred to as half
frequency whirl, occurs at approximately half the rotation
frequency of shaft 110 . This half frequency whirl vibration in
spindle motor 106 causes radial motion of disc 114 that is equal in
magnitude and phase to the half frequency whirl. Additionally, when
head 116, supported by actuator 118, follows a track such as 117,
actuator movement equal in magnitude and phase to the half
frequency whirl takes place in order to maintain proper position of
head 116 over track 117 when disc 114 is radially displaced due to
half frequency whirl vibrations in spindle motor 106.
[0023] Under the present invention, measurement apparatus 100
detects vibration signals produced at transducer head 116 while
transducer head 116 follows track 117 and determines the half
frequency whirl as a function of the detected vibration signals.
Measurement apparatus 100 includes a vibration sensor 102 that
detects vibration signals produced at transducer head 116. Further,
apparatus 100 includes an analyzer 104, coupled to vibration sensor
102, which provides an output that includes the half frequency
whirl magnitude. Analyzer 104 is preferably a spectrum analyzer
that can provide a frequency spectrum of vibrations detected by
sensor 102. Since the frequency of rotation of the spindle motor is
typically known, the magnitude of vibration that corresponds to
half the frequency of rotation of the spindle motor (half frequency
whirl magnitude) can be simply read from the frequency spectrum. In
some embodiments, a processor 105 is coupled to analyzer 104 to
determine the half frequency whirl magnitude from the frequency
spectrum. Further, processor 105 can compare the determined half
frequency whirl magnitude with a threshold half frequency whirl
magnitude and output information indicating whether the determined
half frequency whirl magnitude corresponding to the spindle motor
under test is above or below the threshold half frequency whirl
magnitude. Such a comparison between a measured and threshold value
of half frequency whirl is useful for design verification, quality
assurance and failure analysis of spindle motors.
[0024] Vibration sensor 102 may be either coupled to or positioned
near slider 116 or actuator 118. Preferably vibration sensor 102 is
a non-contact sensor that may by positioned near either slider 116
or actuator 118. In some embodiments, vibration sensor 102 is a
non-contact vibrometer, such as a Laser Doppler Vibrometer (LDV),
which in general senses vibration by detecting variations in
patterns of reflected waves from a vibrating object. A wave source
such as a laser delivers wave radiation to the object whose
vibration is to be measured. The surface of the object reflects the
wave radiation as a speckle interference pattern which is detected
by a detector, such as a photodetector. As the object vibrates, the
speckle interference pattern moves. The variation in the speckle
interference pattern across the detector carries amplitude and
frequency information regarding the vibrating object. In some
embodiments of the present invention, vibration sensor 102 is a
non-contact vibrometer that delivers wave radiation to a mirror 107
(FIG. 1-2) , which is mounted on actuator 118 to provide better
reflection of waves. More accurate measurements from vibration
sensor 102 are obtained when mirror 107 is employed to reflect the
waves. In some embodiments of the present invention, vibration
sensor 102 is a non-contact vibrometer which may be located at a
distance of more than 10 centimeters from the vibrating object such
as actuator 118.
[0025] Referring now to FIG. 2-1, a perspective view of a disc
drive 200 and a vibration measurement apparatus 100 of the present
invention are shown. Disc drive 200 includes a housing with a base
202 and a top cover (not shown). Disc drive 200 further includes a
disc pack 114, which is mounted on a rotor shaft 106 of a spindle
motor by a disc clamp 204. Disc pack 114 includes a plurality of
individual discs. Each disc surface has an associated disc head
slider 116 which is mounted to disc drive 200 for communication
with the disc surface. In the example shown in FIG. 1, sliders 116
are supported by suspensions 206 which are in turn attached to
track accessing arms 208. Suspensions 206 and track accessing arms
208 are part of an actuator 118. The actuator shown in FIG. 1 is of
the type known as a rotary moving coil actuator and includes a
voice coil motor (VCM), shown generally at 210. Voice coil motor
210 rotates track accessing arms 208 with attached suspensions 206
and heads 116 about a pivot shaft 212 to position heads 116 over a
desired data track such as 117. Voice coil motor 210 is driven by
servo electronics 214 based on signals generated by heads 116 and a
host computer (not shown). Vibration measurement apparatus 100 is
employed to determine half frequency whirl of the spindle motor
included in disc drive 200 as described below in connection with
FIGS. 2-2,2-3 and 2-5.
[0026] Referring now to FIG. 2-2, a block diagram of a servo loop
250 in disc drive 200 is shown. Servo loop 250 includes a servo
controller 252 having a gain C and disc drive actuator mechanics
254 having a gain P. Servo controller 252 is the servo controller
circuitry within internal circuit 214 of FIG. 2-1. Drive actuator
mechanics 254 includes actuator assembly 118 and sliders 116 of
FIG. 2-1.
[0027] Servo controller 252 generates a control signal 256 that
drives the actuator mechanics 254. In response, actuator mechanics
254 produces head motion, y, represented by reference numeral 258.
Head motion y is measured by vibration sensor 102. The difference
between head motion y and the rotor shaft motion or disc motion, d,
represented by reference numeral 260, results in the head's servo
measurement signal 262. Servo measurement signal 262 is subtracted
from reference signal 264 to produce a position error signal (PES)
266, which is input to servo controller 252.
[0028] In servo loop 250 of FIG. 2-2, the relationship between head
or actuator motion y and rotor shaft or disc vibration d is 1 y = d
PC 1 + PC or d = y 1 + PC PC Equation 1
[0029] where 2 1 1 + PC
[0030] is the sensitivity function of servo loop 250. FIG. 2-3 is a
plot 270 of the sensitivity function with vertical axis 272
representing gain in decibels (dB) and horizontal axis 274
representing frequency in Hertz (Hz). As can be seen in FIG. 2-3,
the sensitivity function at low frequencies is less than -40 dB.
Half the frequency of rotation of shaft 110 falls within this low
frequency range. When the sensitivity function value is less than
-40 dB, .vertline.PC.vertline. is greater than 100. Thus, at low
frequencies
.apprxeq.d Equation 2
[0031] This demonstrates that accurate measurements of half
frequency whirl in a disc drive spindle motor can be obtained by
measuring actuator motion y. Measurement of half frequency whirl in
the spindle motor of disc drive 200 is carried out using vibration
measurement apparatus 100 when disc drive 200 is energized and
while actuator 118 is following track 117 under the control of
servo electronics 214. The half frequency whirl measurements are
obtained in a manner substantially similar to that described above
in connection with spindle motor 106 of FIG. 1-1.
[0032] FIG. 2-4 is a frequency spectrum 280 obtained as a result of
utilizing proximity displacement probes to measure radial motion at
the outer diameter or edge of discs 114 of disc drive 200.
Frequency spectrum 280 shows variation of vibration amplitude 282
in micro inches (.mu. inches) as a function of frequency 284 in Hz.
Half frequency whirl vibration is shown approximately at region 206
in frequency spectrum 280. As mentioned above, due to disc
manufacturing and assembling errors, such as imperfection in disc
roundness and misalignment between the disc and the rotor shaft,
the proximity displacement probes sense additional low frequency
vibrations that do not emanate from the spindle motor. Due to these
additional vibrations detected at the edges of the discs, the half
frequency whirl amplitude is not clear from frequency spectrum 280
obtained using this prior art technique.
[0033] FIG. 2-5 is a frequency spectrum 290 obtained by utilizing
vibration measurement apparatus 100 of the present invention and
positioning vibration sensor 102 of apparatus 100 at transducer
head 116 of disc drive 200 while it follows track 117. In spectrum
290, the half frequency whirl is shown clearly at region 292. The
clarity of the half frequency whirl amplitude 292 is because the
additional vibrations mentioned above are absent at transducer head
110 and therefore do not appear on frequency spectrum 290.
[0034] Referring now to FIG. 3, a perspective view of a spin-stand
300 and a vibration measurement apparatus 100 of the present
invention are shown. Spin-stand 300 includes a disc 114 which is
mounted on spindle or shaft 110 of a spindle motor 106. Spindle
motor 106 rests on platform 302 which moves between guide rails 304
and 306. Platform 302 can be supported by a cushion of air during
movement and can be stabilized in a particular position by the
application of a vacuum between platform 302 and granite base 308
located directly below platform 302. For purposes of reference,
movement of platform 302 along guide rails 304 and 306 is
considered to be in the "X" direction as shown by arrows 310. A
position encoder 312 can be located, for example, along guide 304
to provide an indication of the position of platform 302.
[0035] Spin-stand 300 also includes a carriage 314 that moves
between rails 316 and 318 in the "Y" direction as indicated by
arrows 320. Similar to platform 302, carriage 314 can be supported
by a cushion of air during movement and can be locked into position
by applying a vacuum between carriage 314 and granite base 308. A
position encoder 322 can be located, for example, along guide 318
to provide an indication of the position of carriage 314.
[0036] Carriage 314 and platform 302 both move using electromotive
motors mounted between one of the guide rails and the respective
platform or carriage. Other types of motors, such as a stepper
motor, may be used in place of the electromotive motors. These
motors generally perform coarse adjustment of a suspension or
actuator assembly 118, which is connected to a suspension chuck 324
and supports a transducing head 116 proximate a surface of disc
114. In one embodiment, suspension chuck 324 is connected to piezo
platform 326 through piezo elements that are able to move
suspension chuck 324, generally in the "X" direction 310, to
perform fine adjustment of transducing head 116 relative to disc
114.
[0037] During head loading operations, pivot motor 328 rotates
eccentric 20 cam 330 causing the back end of pivoting platform 332
to rotate upward about pivot pins 334 and 336. Carriage 314 can be
moved forward so that transducing head 116, carried at the end of
suspension or actuator assembly 118, moves under the spinning disc
114. Support platform 302 is also moved so that the head 116 is
positioned at a desired radius along disc 114. When head 116 nears
the desired location relative to disc 114, motor 328 rotates
eccentric cam 330 back so that pivoting platform 166 returns to its
level position and the head is brought into proximity with disc 114
so that head 116 can fly over the surface of disc 114.
[0038] Head 116 on suspension or actuator assembly 118 is connected
by electrical leads to printed circuit 338, which has further
connections to control box 340. Control circuitry, which is either
part of circuit 338 or contained in control box 340, is used to
control the positioning of head 116 on suspension assembly 118. The
control circuitry for spin-stand 300 can move head 116 to a test
track 117 on disc 116 which data is to be read from or written to.
Additionally, the position of head 116 can be adjusted by the
control circuitry to move head 116 to a number of different
locations within the test track during readback, so that a profile
of head 114 can be determined. Closed loop servo control techniques
can be employed to position head 116 over track 117 during track
following. Measurement of half frequency whirl in the spindle motor
of spin stand 300 is carried out using vibration measurement
apparatus 100 in a manner substantially similar to that described
above in connection with spindle motor 106 of FIG. 1-1.
[0039] FIG. 4 is a flow chart representing a method of indirectly
measuring half frequency whirl in a spindle motor in accordance
with an illustrative embodiment of the present invention. The
spindle motor includes a rotor that can rotate a disc that includes
a track. A transducer head, which is actuated by a control system,
can follow the track when the rotor and disc rotate. At step 402,
vibration signals produced at the transducer head while the
transducer head follows the track are detected. At step 404, the
half frequency whirl is determined as a function of the detected
vibration signals. Different techniques, some of which are set
forth above, can be employed to carry out the steps shown in the
flow chart of FIG. 4 while maintaining substantially the same
functionality without department from the scope and spirit of the
present invention.
[0040] In summary, a method of indirectly measuring half frequency
whirl in a spindle motor (such as 106) having a rotor (such as 110)
adapted to rotate a disc (such as 114) having a track (such as 117)
which is followed by a transducer head (such as 116) that is
actuated by a control system is provided. Vibration signals
produced at the transducer head (such as 116) while the transducer
head (such as 116) follows the track (such as 117) are detected.
The half frequency whirl is determined as a function of the
detected vibration signals.
[0041] It is to be understood that even though numerous
characteristics and advantages of various embodiments of the
invention have been set forth in the foregoing description,
together with details of the structure and function of various
embodiments of the invention, this disclosure is illustrative only,
and changes may be made in detail, especially in matters of
structure and arrangement of parts within the principles of the
present invention to the full extent indicated by the broad general
meaning of the terms in which the appended claims are expressed.
For example, the particular elements may vary depending on the
particular application for the spindle motor while maintaining
substantially the same functionality without departing from the
scope and spirit of the present invention. In addition, although
the preferred embodiment described herein is directed to a spindle
motor for disc drives and spin-stand testers, it will be
appreciated by those skilled in the art that the teachings of the
present invention can be applied to other systems that employ
spindle motors, without departing from the scope and spirit of the
present invention.
* * * * *